The digital enhanced cordless telecommunications (DECT) standard is a wireless air interface and communication protocol designed to provide wireless communications for telecommunications equipment such as cordless phones. The DECT standard is promulgated by the European Telecommunications Standards Institute. It operates in the 1.8 GHz radio band, employing Time Division Multiple Access (TDMA) technology. DECT operates at speeds of 2 Mbps and is ideal for use in voice applications. DECT offers the advantages of low power consumption, enabling smaller batteries to be used in a wireless headset.
The use of Wireless Local Area Networks (WLANs) has recently increased. In particular, the IEEE 802.11 series of WLAN specifications have gained widespread acceptance. IEEE 802.11 wireless LAN's are becoming pervasive throughout the industry. It is desirable to be able to use IEEE 802.11 (“802.11”) standardized networks to transmit voice either within an enterprise (intranet) or over a wider area (internet) using VoIP technologies or converging the LAN with the telephony system within a company to provide wireless access to the public switched telephone network (PSTN) system. In addition, many applications exist for a wireless voice connection of high quality to a PC for a variety of applications.
The IEEE 802.11 wireless LAN standard addresses the basic transport of LAN data over a wireless medium. There are currently three variations of 802.11: IEEE 802.11a (5 GHz, 54 Mbps), IEEE 802.11b (2.4 GHz, 11 Mbps), and IEEE 802.11g (2.4 GHz, 54 Mbps). Streaming media applications, such as voice communication require a reliable and predictable data stream. Such reliability and predictability is provided by the ability to classify traffic and prioritize time-sensitive classes of traffic, referred to as QoS (Quality of Service). QoS is addressed by 802.11e. It includes more effective channel management, provides better power management for low power devices, specifies a means to set up side links to other 802.11 devices while simultaneously communicating with an 802.11 AP, and provides improvements to the polling algorithms used by access points.
Referring to FIG. 5, a prior art 802.11 LAN is illustrated. A distribution system 502, also referred to as a backbone, is used to forward frames to their destination when several access points are connected to form a large coverage area, requiring communication between each access point to track the movements of mobile stations. In many embodiments Ethernet is utilized. Access points 504, 506 act as bridges between the wireless world and the wired world. Each access point has at least two network interfaces: a wireless interface that understands 802.11 and a second interface with wired networks. Typically, the wired interface is an Ethernet port and/or WAN port. Access points typically have a TCP/IP interface. Stations 508, 510 are computing devices with wireless network interfaces, typically laptops or handheld computers. Stations 508, 510, can also be computers not intended to be portable, such as desktops. Wireless medium 512 is utilized to move frames from stations 508, 510 to access point 504, 506 with radio frequency layers being used in typical embodiments.
However, the use of 802.11 directly to transmit voice between a wireless telephonic device, such as a wireless headset, and an access point is problematic. 802.11 requires higher power relative to lower power RF protocols such as DECT, necessitating the use of large batteries that add to the weight, space, and size of the headset. In order to implement 802.11 in a headset, power issues become paramount. It is difficult to make a headset that is wearable while retaining high QoS because of these problems. In addition, there usually is not enough space on the headset proper to fit dial pads. Range vs. density is an issue with present day systems. It is desirable to have as much range as possible; in fact, it is desirable to be able to wander anywhere in a building or buildings and be able to continue a conversation. By their very nature, it is not possible to obtain substantial range (e.g., greater than 50 to 100 meters) without transmitting a lot of power (which rapidly bumps into limits placed on total power by the FCC). This in its self limits range. Furthermore, as one uses more power to get range, then the bandwidth available (allocated bandwidth by the FCC or other governmental agency) becomes insufficient to support all of the traffic from multiple users. Thus, the range vs. density problem arises. If more range is desired, then fewer users can be accommodated because of interference issues.
The range vs. density problem is usually not solved with standard cordless systems without special hardware. The use of cells and roaming is the classical way that this problem is solved and is done extensively by the cell phone industry. When density becomes too great, more cell sites are added and the power from any one transmitter is reduced. This preserves the range (through roaming) and increases density because power is reduced which reduces interference. The 802.11 system inherently provides roaming capability so a voice data system based on 802.11 can solve this problem.
However, the use of 802.11 in a wireless telephonic device such as a headset is problematic. The use of an 802.11 link in a telephonic device such as a headset has the problem of requiring a very large battery in the headset to support normal talk times. Audio quality is usually compromised because of the need for battery conservation. For example, one battery conservation solution currently used is to buffer up to 40 msecs of data, and then “blast” it out in about 4 msecs. The power is then turned off for 36 msec saving a considerable amount of power. However, this is done at the expanse of adding 36 msec of delay. From a QoS point of view, this is undesirable. Power problems are even greater for higher bit rate 802.11a and 802.11g relative to 802.11b.
In addition, if one wanted to get audio into a computer, it would have to go through at least two hops; one from the headset to an access point, and another from the access point back to the computer. This also adds undesirable delay. It also doubles the required number of bits, reducing network capacity and thereby decreasing density capability. Although Ad hoc links are possible, they are not usually supported for other reasons.
Thus, there has been a need for improvements in wireless network architectures and the use of wireless telephonic devices. More specifically, there has been a need for improved systems and methods for the use of 802.11 wireless networks and wireless telephonic devices.